Zirconium phosphate (ZP) solid particles are used as ion-exchange materials and are particularly useful as a sorbent material in sorbent cartridges used for regeneration of dialysis solution. For instance, a sorbent cartridge containing ZP ion-exchange materials and other dialysate treatment components have been used for the REDY (REgenerative DialYsis) system. FIG. 1 shows various functions of each layer in a REDY cartridge, inclusive of zirconium phosphate. Among its functions, this commercial apparatus utilizes zirconium phosphate to remove the ammonia produced by the enzymatic decomposition of urea in the presence of urease contained in the cartridge. The regeneration efficiency of the zirconium phosphate, and hence the entire cartridge, typically decreases over time of use, for example, through deactivation by adsorbed ions, the presence or accumulation of materials that were not originally present in the layer, or other factors. It has been reported that the spent zirconium phosphate adsorbent is not regeneratable and must be discarded, such as indicated in U.S. Pat. No. 4,094,775. The used or spent zirconium phosphate is discarded and the entire sorbent cartridge may be replaced with a fresh cartridge to restore the function.
Methods for regeneration of sorbent materials have been proposed, for example, as shown in some published patent documents.
U.S. Pat. No. 7,052,609 relates to regeneration of adsorbent matrices that are used for the purification of substances from aqueous liquid samples derived from biological material. The method of the '609 patent is adapted to adsorbent matrices that are sensitive to hydrolysis either because of a sensitive base matrix or a sensitive ligand including also a sensitive spacer and is characterized in contacting at least one regeneration solution with the adsorbent matrix which comprises an organic solvent which is water-miscible and has a pH value ≦4, preferably ≦3 (acid solution) or ≧10 but <13 (alkaline solution).
U.S. Patent Application Publication No. 2001/0008617 relates to a process for recovering a metal from a metal-containing material, which uses sulfuric acid and/or an organic acid to regenerate spent sorbent from a metal recovery process. The process of the '617 published patent application relates generally to the regeneration of sorbents used for metal removal, and specifically to the regeneration of carbonaceous sorbents such as activated carbon.
U.S. Pat. No. 8,187,991 relates to a method of regenerating adsorbent material which includes providing a spent adsorbent material and contacting the adsorbent material with a solvent composition to facilitate removing oil and impurities from the spent solvent material.
U.S. Pat. No. 8,173,566 relates to a method and apparatus for regenerating a sorbent that has been poisoned by components derived from flue gas. In the method of the '566 patent, the sorbent is treated with an agent to remove the poisoning components and introduce a promoting agent into the sorbent.
WO 2012/047142 relates to a method for the removal of arsenic in a positive oxidation stage from an aqueous liquid. In the method of WO '142, an adsorbent that is used in the method that comprises a solid phase carrying a metal ion capable of binding arsenic is optionally regenerated and re-used.
The present investigators have recognized the need to improve the current sorbent dialysis technology and its accompanying treatment modalities. One such improvement is the regeneration or “recycle” of the spent sorbent material in the cartridge, such as for example, the zirconium phosphate. The investigators further have recognized that there is a need for sorbent cartridges for dialysis systems and/or other filtering systems that can effectively use such regenerated spent zirconium phosphate.